The officers, in a Porsche 911 Carrera and a Subaru Impreza 2000 Turbo, were on duty at the time but not responding to an emergency.

Pc Sam Short, 32, of Camberley was on the way to a home visit after his partner gave birth to a baby and his pal Pc Azim Choudry, 28, was in hot pursuit.

Their alleged race came to a halt when Choudry lost control of the Porsche and smashed into a tree.

The court heard how Choudry miraculously escaped with only minor injuries. Short in the Subaru was unhurt.

The Metropolitan Police officers appeared at Guildford Crown Court where they both denied dangerous driving.

Richard Bendall, prosecuting, told the court the incident happened on July 27 2004 on the A316 near Sunbury, Middlesex.

Mr Bendall said motorist Philip Jones, who was driving a Renault Espace at 60-65mph, saw the cars race past him.

He said: “At that stage he was overtaken by a blue Subaru. Both he and his passenger estimate that the Subaru was travelling in excess of 100mph. The exact speed was impossible to assess but Mr Jones described the Subaru as overtaking ‘as if I was standing still’.

“No more than a second later he saw a second vehicle follow it — this time a silver Porsche that was travelling at a similar speed and very close to the car in front. Mr Jones estimates that it was no more than 12 feet behind.

“The Subaru moved into the middle lane and the Porsche followed doing exactly the same.

“At the next exit at the very last minute, the Subaru, without indicating, veered from the middle lane on to the slip road and left the A316.

“The Porsche attempted to do the same thing and completely misjudged it. It crashed into the barrier went airborne and continued into a street light.

“It knocked that over then hit a tree about five feet from the ground. It crashed to the floor in a cloud of dust.

“The Porsche driver had taken the turning far too late and far too fast.”

Mr Bendall said Choudry had to be cut from the wreckage but suffered only minor injuries.

The court heard Short had parked his car near the scene and was wandering around.

Mr Bendall said: “The police arrived and the witnesses gave their account of what happened.

“They were approached by the driver of the Subaru who was asking them what they had said to the police.

“Mr Phillip Jones said they had told them what they had seen, that they were speeding and racing. The driver said ‘we weren’t speeding’ and then walked off.”

An accident investigator said the nature of the skid marks indicated that the Porsche, which suffered no mechanical failure, was out of control and travelling sideways off the road, the court heard.

Mr Bendall said subsequent attempts to interview the pair failed. Choudry handed in a written statement saying he was following his friend to the address and had lost control.

Mr Bendall said: “They were obviously racing and that racing was equally as irresponsible and equally as dangerous as the speed itself.

“Both were fortunate that no one was seriously injured - neither a member of the public nor one of them.

“It is plain they were racing and both grossly exceeding the speed limit in a highly dangerous fashion.”

Mr Jones told the jury how the cars sped past him. He said: “It was quite dangerous driving in a way. It looked like they were racing because of what happened next.

“It (the Porsche) hit the barrier, hit the lamppost then hit the tree, then the ground.

There was an almighty noise when it hit the tree, like a plane taking off.”

Cross-examined by Heather Stangoe for Short, Mr Jones denied there was any chance that the two cars were in fact 100-200ft apart. She asked whether it was the modified exhaust that caused Mr Jones to notice the car.

But Mr Jones said: “I would disagree. I think a car that’s electric blue in colour and overtakes you at speed is quite noticeable without the exhaust.”

Short of Roxburgh Close, Camberley, and Choudry, from Forest Gate, East London, both deny the charges.